1. Field of the Invention
The present invention relates to a broadcasting terminal and, more particularly, to a portable satellite multimedia broadcasting terminal and method for updating pilot channel information.
2. Description of the Related Art
Recently, mobile communication terminals, such as a portable multimedia broadcasting terminal, a PDA (Personal Digital Assistant) terminal or a smart terminal, have been developed to provide various functions. Among the various functions, support of digital multimedia broadcasting covering audio, video and data services has been actively developed.
FIG. 1 illustrates an overview of one example of a conventional satellite multimedia broadcast system 1 that utilizes a DMB (Digital Multimedia Broadcasting) station 2 and a DMB terminal 3 and a mobile phone 4 with a DMB receiver. The satellite multimedia broadcasting system 1 allows a mobile user to receive multimedia information or data via the satellite multimedia broadcasting terminal 3 or DMB receiver equipped mobile phone 4.
Multimedia broadcasting systems have been separately developed as a terrestrial multimedia broadcasting system and a satellite multimedia broadcasting system. The satellite multimedia broadcasting system is classified as one of a system A, a system Dh and a system E. A system E satellite multimedia broadcasting system employs a CDM (Code Division Multiplexing) method and is applied to satellite multimedia broadcasting.
A satellite multimedia broadcasting system adopting the CDM method can operate a satellite multimedia broadcasting terminal with CDM channel configuration information. The CDM channel configuration information is included in pilot channel information. The pilot channel information refers to information regarding the analysis of reception signals, synchronization detection of spread signals, and control of the receiver as well as CDM channel configuration information.
The pilot channel information is transferred to the satellite multimedia broadcasting terminal through a pilot channel. Therefore, if the satellite multimedia broadcasting terminal fails to properly receive the pilot channel information included in the pilot channel, the terminal cannot be operated. Furthermore, if the pilot channel information included in the pilot channel transmitted by a broadcast station is changed, the pilot channel must be updated according to the changed pilot channel information so that the satellite multimedia broadcasting terminal can smoothly receive a broadcast service and operate properly. Accordingly, when a first processor at a receiving end of the satellite multimedia broadcasting terminal obtains pilot channel information at a pre-set period and provides the pilot channel information to a second processor, the second processor updates the pilot channel information.
FIG. 2 illustrates a flow chart of a conventional method for updating pilot channel information by a satellite multimedia broadcasting terminal. As illustrated in FIG. 2, when a pilot channel information period is set (step S11) and a satellite multimedia broadcasting terminal is operated (step S12), the first processor obtains pilot channel information (step S13). The first processor obtains pilot channel information at every pre-set period and transfers the pilot channel information to the second processor (step S14). The second processor checks the version number of the pilot channel information (step S15), and if there is a change in the version number (step S16), the second processor updates the pilot channel information (step S17).
Specifically, in the process illustrated in FIG. 2, the second processor determines whether to update the pilot channel information according to the pilot channel information received every pre-set period. If the version number of the pilot channel information has changed, the second processor updates the pilot channel information.
The time period at which the pilot channel information is updated by the second processor has a significant effect on a system. A first processor, such as a pilot channel information processing unit provided by the TOSHIBA™ corporation, obtains pilot channel information at a rate of at least every super frame period (76.5 ms) up to a maximum of every 16 super frame periods (1,224 ms) and unconditionally transfers the pilot channel information to a second processor, such as a CPU (Central Processing Unit), regardless of whether or not the pilot channel information has changed.
FIG. 3 illustrates the construction of a conventional transmission frame of a typical pilot channel. One frame has a length of 12.75 ms and includes pilot symbols (PS) of successive ones (11, . . . , 1) and a pilot channel data portion of Dns (D1˜D51, n=1, 2, . . . , 51). Payload data, including actual information of a pilot channel, is contained in D3˜D22 and D27˜D46, and other pilot channel data has a specific value or a check value, such as Reed-Solomon parity check bits.
As illustrated, six frames form one super frame and one super frame has the length of 76.5 ms. Since pilot channel information is transferred to the second processor at such a relatively short time period and the second processor must perform the processes of receiving and comparing pilot channel information with existing pilot channel information every corresponding time period, the control burden of the second processor increases.
Specifically, the second processor must continuously receive the pilot channel information and compare it with the existing information even while processing an input of the user, performing an operation related to a user interface or performing an operation required for operating the broadcast receiver. Therefore, the second processor must facilitate high performance at a relatively high clock speed.
The pilot channel information is not changed unless a channel is changed or a broadcast operation is changed according to the management of a broadcasting service. However, because the pilot channel information is the most preferential reference information in the satellite multimedia broadcasting broadcast system, the system must be sensitive in its reacting to changes in the pilot channel information.
In the conventional method, the pilot channel information is obtained by the pilot channel information processing unit according to a relatively short period of from one super frame to approximately 16 super frames and is provided to the second processor of the satellite multimedia broadcasting terminal regardless of whether the pilot channel information has changed. The second processor then interprets the received new pilot channel information to determine whether the currently used pilot channel information has been changed. When there is a change in the pilot channel information, the second processor updates the existing content at every time period each, thereby increasing the operational burden of the second processor.
Therefore, there is a need for a satellite multimedia broadcasting terminal and method for updating pilot channel information that facilitates more efficient transfer of pilot channel information such that the operational burden of the second processor is decreased.